Sitting too long raises risk of early death from all causes, study finds

By gerencherk

Attention, desk jockeys and couch potatoes. Going to the gym can be good exercise, but it may not be enough to counteract a rising public-health threat: sitting in one place for too long.

Scientists have long known that sedentary lifestyles lead to health risks like weight gain, obesity and type 2 diabetes. But a new study found that sitting six or more hours a day increased the risk of early death from all causes by an average 35% for women and 18% for men — even if you exercise.

Researchers from the American Cancer Society compared a large group of long-time sitters to people who sat less than three hours a day and controlled for factors like smoking. Death from heart disease was the biggest risk associated with prolonged sitting, and again women were more vulnerable. See the study’s abstract here.

Women who sat more than six hours a day faced a 33% higher risk of early death from cardiovascular disease compared with women who sat fewer than three hours a day. Long-sitting men had an 18% increased risk of premature death from heart disease.

In cancer, there was a 30% higher risk of early in women who sat the longest compared with women who sat the least. There was no indication of increased cancer risk among men who sat the longest.

Failing to exercise plus sitting for long stretches proved even more hazardous. The combination of little physical activity and long periods of sitting was linked to a 94% higher risk of premature death for women and a 48% higher risk for men compared with those who sat the least and exercised the most.

Researchers hypothesize that uninterrupted sitting can cause large muscle groups to shut down and lead to damaging metabolic changes, said Alpa Patel, an epidemiologist for the American Cancer Society in Atlanta and lead author of the study, which was published in the American Journal of Epidemiology.

For the study, about 125,000 people, mostly retired or unemployed, reported how they spent their leisure time between 1993 and 2006. During that time, 11,307 men died and 7,923 women died.

Researchers are building a body of evidence that should prompt public-health messages to include the benefits of reduced sitting time in addition to those derived from physical activity, Patel said.

The findings about the health risks of prolonged sitting raise many questions for future research. Among them: What implications could they have for women’s longer life expectancy compared with men? If more women are working jobs that require them to be sedentary most of the day, will that lack of daily mobility start to erode their average five-year longevity advantage over men?

Another question is whether the effects of prolonged sitting are reversible.

“We did see the impact sustained over 14 years,” Patel said. But she noted that it’s never too late to quit smoking, be physically active or maintain a healthy weight since rectifying poor health habits late in life can bring some benefits.

“We would hope to see that the same would be true here, but that has not yet been examined,” she said.

Sitting less

So what should you do with this information?

First, if you find yourself sitting for hours on end, interrupt your patterns. Stand up, move around and get your blood flowing at least once an hour.

Second, take the low-tech route. At work, walk over to a colleague instead of relying on email or instant messaging.

Finally, increase your steps. Take the stairs instead of the elevator. Buy a pedometer or just try to walk more in general. You’ll reduce the amount of sitting you do and work in some physical activity at the same time.

About Health Matters

Health Matters is a blog-style round-up of news and analysis concerning consumer health and the business of health care. The lead writer is MarketWatch reporter Kristen Gerencher, who also writes the Vital Signs column. Andrea Coombes and Jonathan Burton contribute editing. Gerencher won a 2006 explanatory journalism award from the Society of Professional Journalists-Northern California for a series she did on health savings accounts.